I've been cooking it for a couple of evenings and got it up to 0.6V @ 40C so decided to give it a try.
Hooked up a speaker into the right channel and tried to play Radio Paradise from my phone - nothing - after about 10 secs start getting the "something's hot" smell and then smoke escaped.
Turns out it's R14 on the _left_ channel that has burnt - but R7 and R8 look like they've got hot as well 🙁
Will dissasemble later and see what I can find, but any ideas on what may have happened?
Hooked up a speaker into the right channel and tried to play Radio Paradise from my phone - nothing - after about 10 secs start getting the "something's hot" smell and then smoke escaped.
Turns out it's R14 on the _left_ channel that has burnt - but R7 and R8 look like they've got hot as well 🙁
Will dissasemble later and see what I can find, but any ideas on what may have happened?
Are you speakers ok? Any change of dc offset at the source?
Also, can you verify what value you used for R13 and R14? I'm wondering
if it might be oscillation. Hopefully others will chime in.
Also, can you verify what value you used for R13 and R14? I'm wondering
if it might be oscillation. Hopefully others will chime in.
Last edited:
I only had one speaker to hand - plugged into the Right channel. Left has burnt.
Speaker itself is fine, protection relay clicked on OK so I don't think anything amiss there.
Only thing different on Left channel was that I did have the input from phone plugged in.
Before I plugged the speaker in it had ben powered up a couple of hours. Temps were same as they were last night when I had last measured R7/R8 before replacing the lid.
Speaker itself is fine, protection relay clicked on OK so I don't think anything amiss there.
Only thing different on Left channel was that I did have the input from phone plugged in.
Before I plugged the speaker in it had ben powered up a couple of hours. Temps were same as they were last night when I had last measured R7/R8 before replacing the lid.
A view of the burnt R14 and one of the singed 3W 0.47R resistors. I'll swap these out but would it be prudent to swap out the IRFP240 as well? I guess I would need to order a pair from the DIYAudio store which could take a while to materialise.
I'm listening out of the Right channel now anyway, so that's something...
I'm listening out of the Right channel now anyway, so that's something...
I hade that happen with a rather primitive tube preamp feeding the F5. Your jfets/mosfets may be toast.
I'm confused.
When you left channel blew, did you have the speaker on the right channel, but input on the left? And since you heard nothing, you cranked the input up high?
Please post photos as 6L6 suggested.
When you left channel blew, did you have the speaker on the right channel, but input on the left? And since you heard nothing, you cranked the input up high?
Please post photos as 6L6 suggested.
Just smoke and no sound. No speaker damage. I bought some caps to put across the mosfets but haven't gotten around to installing them yet. I never used that tube amp again and haven't had any issues for years.
JFets and Mosfets show no sign of heat damage or blistering.
Other than the charred R7 and R8 there's not much to see, it's out now and burnt components removed. It had biased up correctly.
Speaker out was on the right channel only. 3.5mm minijack to RCA splitter, but connected to both inputs.
There was no output to the speaker before the smoke, but the speaker protect came on. It may have been input thump of connecting the minijack into the phone socket that put the speaker protect on.
Other than the charred R7 and R8 there's not much to see, it's out now and burnt components removed. It had biased up correctly.
Speaker out was on the right channel only. 3.5mm minijack to RCA splitter, but connected to both inputs.
There was no output to the speaker before the smoke, but the speaker protect came on. It may have been input thump of connecting the minijack into the phone socket that put the speaker protect on.
Generally speaking you always turn on the source before the pre and the pre before the power amp. This prevents these things from happening.
Yep, realising that now 😱
I spend so long going back and forth through these threads and then I manage to find a new way to break things.
I guess I need to remove the mosfets to check if they're OK and my solder sucker just fell apart as well 🙁
Hopefully you can easily put the solder sucker back together. Mine falls apart
from time to time also.
At least the speaker is ok and a couple resistors and maybe a mosfet aren't too bad as damages go.
Hang in there. You'll get it sorted out.
from time to time also.
At least the speaker is ok and a couple resistors and maybe a mosfet aren't too bad as damages go.
Hang in there. You'll get it sorted out.
Thanks Dennis.
Now I'm wondering...if I need to get stuff shipped from the US shall I order enough for the F5-T 😉
Now I'm wondering...if I need to get stuff shipped from the US shall I order enough for the F5-T 😉
So sorry to hear of the troubles. I remember when people kept telling me that releasing the magic smoke was a right of passage. I thought at the time, how foolish, I'll always be careful and build things properly. HA! 😀
If you're thinking of ordering another set of new MOSFETs from the DIYA store you could consider ordering and matching your own parts. If you're already contemplating an F5T, my guess is other FWs may be in your future too.
It took me a bit to understand the simple schematic and create my little jig, but you could likely do it much faster than I. Once I got the hang of it, I could measure and sort a tube in less than an hour to my level of satisfaction. I admit that I am not hyper-picky about it. So far, evidence suggests that I've done it well enough.
+1 to Dennis. You'll get it, and more importantly, you'll love it.
If you're thinking of ordering another set of new MOSFETs from the DIYA store you could consider ordering and matching your own parts. If you're already contemplating an F5T, my guess is other FWs may be in your future too.
It took me a bit to understand the simple schematic and create my little jig, but you could likely do it much faster than I. Once I got the hang of it, I could measure and sort a tube in less than an hour to my level of satisfaction. I admit that I am not hyper-picky about it. So far, evidence suggests that I've done it well enough.
+1 to Dennis. You'll get it, and more importantly, you'll love it.
Well, after some decorating, building a new rack (both pictured) and Christmas, and getting hold of some Mosfets (with an M2X) I put everything back together without mishap this time and have had it on test - very pleased so far but there is a miniscule amount of hum I need to track down. Thanks for all your help! 😀
F5 2018 R values
Hello all!!
After build Aleph J I can't stop... and now I'm building the F5, but I found differences between F5 V3.0 version pcb with pdf building guide. According the differences, I have to respect resistor values of the pdf though aren't same "R number" un pcb really ?? Because I see the schema are the same only added the P3....
Hello all!!
After build Aleph J I can't stop... and now I'm building the F5, but I found differences between F5 V3.0 version pcb with pdf building guide. According the differences, I have to respect resistor values of the pdf though aren't same "R number" un pcb really ?? Because I see the schema are the same only added the P3....
Attachments
I looks like you have this build guide, I think.
https://www.diyaudio.com/media/build-guides/diyaudio-f5-build-guide.pdf
Try this one. It should align perfectly with your boards.
Firstwatt F5 amplifier v3 - diyAudio Guides
Enjoy the F5! We will all wonder what you will build after the F5.
https://www.diyaudio.com/media/build-guides/diyaudio-f5-build-guide.pdf
Try this one. It should align perfectly with your boards.
Firstwatt F5 amplifier v3 - diyAudio Guides
Enjoy the F5! We will all wonder what you will build after the F5.